The new gray cups are dialed! I popped one off during the A-main warm-up at the Nationals this year, popped it back on, and ran it for the entire 60 minute main. They're awesome.
If more than one ball-cup pops off of the same stud, it's time to replace the stud. It's best to check your cups and studs before every big race, and before every big race main. As far as club racing goes..I usually let them slide for a long time, haha.